scholarly journals Numerical Investigation of Complex Thermal Coal-Gas Interactions in Coal-Gas Migration

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Xiaoyan Ni ◽  
Peng Gong ◽  
Yi Xue
Keyword(s):  
Coal Seam ◽  
Variable Temperature ◽  
Gas Pressure ◽  
Gas Migration ◽  
Coal Seams ◽  
Coal Seam Gas ◽  
Coal Gas ◽  
Thermal Coal ◽  
Gas Seepage ◽  
Gas Interactions

Understanding the influence of temperature on the gas seepage of coal seams is helpful to achieve the efficient extraction of underground coal seam gas. Thermal coal-gas interactions involve a series of complex interactions between gas and solid coal. Although the interactions between coal and gas have been studied thoroughly, few studies have considered the temperature evolution characteristics of coal seam gas extraction under the condition of variable temperature because of the complexity of the temperature effect on gas drainage. In this study, the fully coupled transient model combines the relationship of gas flow, heat transfer, coal mass deformation, and gas migration under variable temperature conditions and represents an important nonlinear response to gas migration caused by the change of effective stress. Then, this complex model is implemented into a finite element (FE) model and solved through the numerical method. Its reliability was verified by comparing with historical data. Finally, the effect of temperature on coal permeability and gas pressure is studied. The results reveal that the gas pressure in coal fracture is generally higher than that in the matrix blocks. The higher temperature of the coal seam induces the faster increase of the gas pressure. Temperature has a great effect on the gas seepage behavior in the coal seams.

scholarly journals Research and Optimization of Gas Extraction by Crossing-Seam Boreholes from Floor Roadway

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Gang Li ◽  
Jiafei Teng
Keyword(s):  
Coal Seam ◽  
Gas Permeability ◽  
Gas Pressure ◽  
Gas Content ◽  
Gas Extraction ◽  
Gas Migration ◽  
Governing Equations ◽  
Coal Seam Gas ◽  
Gas Seepage ◽  
Gas Disaster

Deep coal seams are characterized by large stress, high gas pressure, and low permeability. The gas disaster threatens the safe production of coal mine seriously. Gas extraction by crossing-seam boreholes from floor roadway (GECMBFR) can reduce the pressure and content of coal seam gas, which is the main measure to prevent gas disaster. Considering the Klinkenberg effect, governing equations of gas adsorption/desorption-diffusion, gas seepage, and stress fields within the coal seam are established to form the seepage-stress coupling model. The governing equations are embodied into a finite element driven software to numerically simulate gas migration and fluid-solid coupling law in coal seam. On this basis, the process of gas extraction under different borehole spacings and diameters is simulated. The effects of these two key parameters on coal seam gas pressure, gas content, and gas permeability were analyzed. The borehole spacing and diameter were determined to be 5 m and 0.09 m, respectively. Combined with the actual situation of a mine, the process of gas extraction from floor roadway with different cross-sectional schemes, ordinary drilling boreholes and punching combined drilling boreholes, is comparatively analyzed. The results show that the gas extraction effect by ordinary drilling boreholes is lower than that of the punching combined drilling boreholes, and the extraction is uneven and makes it difficult to meet the standard. Hydraulic punching was carried out, and coal was washed out of the borehole, which expanded the contact area between the borehole wall and coal seam. The coal seam around the punching borehole is unloaded, which improves coal permeability and accelerates gas migration towards the borehole, thus promoting the efficiency of gas extraction. It is more reasonable to use punching combined drilling borehole scheme when implementing the GECMBFR technology.

scholarly journals A New Method for the Measurement of Gas Pressure in Water-Bearing Coal Seams and Its Application

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Xiao Cui ◽  
Jiayong Zhang ◽  
Liwen Guo ◽  
Xuemin Gong
Keyword(s):  
Coal Seam ◽  
Field Experiments ◽  
Water Pressure ◽  
Direct Methods ◽  
Gas Pressure ◽  
New Method ◽  
Well Testing ◽  
Coal Seams ◽  
Coal Seam Gas ◽  
Gas Disaster

Coal seam gas pressure is one of the fundamental parameters used to assess coal seam gas occurrence and is an important index in assessing the risk of gas disaster. However, the geological characteristics of coal seams become increasingly complex with increasing mining degree, thus decreasing the accuracy and success rate of direct methods for measuring gas pressure. To address such issues, we have developed a new method for direct measurement of gas pressure in water-bearing coal seams. In particular, we developed a pressure measurement device based on theoretical analysis and quantified the basic parameters of the device based on well testing. Then, we verified the applicability of our method based on comparative analysis of the results of field experiments and indirect measurements. Our results demonstrate that this new method can resolve the effects of water pressure, coal slime, and other factors on the estimation of gas pressure. The performance of this new method is considerably better than that of traditional methods. In particular, field test results demonstrate that our method can accurately and efficiently measure gas pressure in water-bearing coal seams. These results will be of great significance in the prevention and control of coal seam gas disaster.

The Application of Crossing and Grid Drainage Boreholes in Floor Tunnel for Coal Roadway Safety Tunneling

2014 ◽  
Vol 962-965 ◽  
pp. 1169-1174
Author(s):  
Hong Qing Zhu ◽  
Bei Fang Gu ◽  
Min Bo Zhang ◽  
Chao Yu ◽  
Zhen Zhang
Keyword(s):  
Coal Seam ◽  
Gas Pressure ◽  
Gas Content ◽  
Dynamic Phenomenon ◽  
Coal Seams ◽  
Coal Seam Gas ◽  
Technical Parameters ◽  
Coal Roadway ◽  
Roadway Safety ◽  
The Relationship

In order to reduce the danger of single coal seams outburst during the tunneling in coal roadway and ensure the tunneling of coal seams, this text analyzed the mechanism of crossing drilling against outburst; studied the area measures of floor tunnel crossing and grid drainage boreholes in coal roadway, Designed and optimized the drilling technical parameters; Analyzed the relationship between the drainage concentration and scalar; Calculated the maximum overlying coal seam gas to spare scalar quantity is 224300 m3 ;Used a variety of indicators to investigate the effect of outburst prevention. It shows that Gas content and gas pressure have significant lower than drainage. After the drainage up to standard, all the sensitive indexes is not overrun, during the coal roadway tunneling, it does not appears dynamic phenomenon. Solve the problem of mining imbalances, guaranteed the safety driving of roadway.

COAL SEAM GAS—PETROLEUM OR MINERAL

1997 ◽  
Vol 37 (1) ◽  
pp. 589
Author(s):  
D.J. Gately
Keyword(s):  
Private Sector ◽  
Coal Seam ◽  
Coalbed Methane ◽  
Resource Development ◽  
Coal Seams ◽  
Coal Seam Gas ◽  
Commercial Use ◽  
Private Sector Investment ◽  
History Of ◽  
Policy Shift

1996 was a watershed year for gas exploration in Queensland: the increasing private sector investment in the search for and commercial use of methane gas from coal seams received legislative endorsement. Coal seam gas (CSG), also known as coalbed methane or CBM, was officially designated as petroleum, with exploration for and production of CSG to be administered under the Petroleum Act.The paper traces the history of exploration for CSG in Queensland since 1976, culminating in a policy shift in 1996. In Queensland there is now potential for overlapping titles and competitive resource development.

scholarly journals Nitrogen Injection To Flush Coal Seam Gas Out Of Coal: An Experimental Study

2015 ◽  
Vol 60 (4) ◽  
pp. 1013-1028 ◽  
Author(s):  
Lei Zhang ◽  
Naj Aziz ◽  
Ting Ren ◽  
Jan Nemcik ◽  
Shihao Tu
Keyword(s):  
Coal Seam ◽  
Clean Energy ◽  
Gas Content ◽  
Coal Seams ◽  
Coal Seam Gas ◽  
Gas Recovery ◽  
Nitrogen Injection ◽  
Gas Desorption ◽  
Effective Role ◽  
Study Laboratory

Abstract Several mines operating in the Bulli seam of the Sydney Basin in NSW, Australia are experiencing difficulties in reducing gas content within the available drainage lead time in various sections of the coal deposit. Increased density of drainage boreholes has proven to be ineffective, particularly in sections of the coal seam rich in CO2. Plus with the increasing worldwide concern on green house gas reduction and clean energy utilisation, significant attention is paid to develop a more practical and economical method of enhancing the gas recovery from coal seams. A technology based on N2 injection was proposed to flush the Coal Seam Gas (CSG) out of coal and enhance the gas drainage process. In this study, laboratory tests on CO2 and CH4 gas recovery from coal by N2 injection are described and results show that N2 flushing has a significant impact on the CO2 and CH4 desorption and removal from coal. During the flushing stage, it was found that N2 flushing plays a more effective role in reducing adsorbed CH4 than CO2. Comparatively, during the desorption stage, the study shows gas desorption after N2 flushing plays a more effective role in reducing adsorbed CO2 than CH4.

Transformation of the Triaxial Seepage Device for Measuring Deformation of Coal Containing Gas

2013 ◽  
Vol 477-478 ◽  
pp. 610-613
Author(s):  
Mei Yuan ◽  
Qing Hao Meng ◽  
Jiang Xu ◽  
Bo Bo Li ◽  
Yu Qin Du
Keyword(s):  
Coal Seam ◽  
Gas Migration ◽  
Coal Deformation ◽  
Gas Seepage

To explore the regularity of deformation and gas migration of coal seam, the author transmits signal of strain foil on coal samples in all directions by transforming oil plug, oil plug seal, heat shrink tubing and wire seal, based on the existing triaxial seepage device. We can complete coal deformation and gas seepage test with this device under different temperature, different stress, different gas stress and so on.

scholarly journals The research of coal seam gas pressure and initial gas emission characteristics of borehole

2019 ◽  
Vol 7 (5) ◽  
pp. 1961-1969 ◽  
Author(s):  
Jianhua Zeng ◽  
Shixiang Tian ◽  
Guiyi Wu ◽  
Yunjun Zuo ◽  
Shiqing Xu ◽  
...  
Keyword(s):  
Coal Seam ◽  
Gas Pressure ◽  
Emission Characteristics ◽  
Coal Seam Gas ◽  
Gas Emission

WATER AND THE COAL SEAM GAS INDUSTRY

2007 ◽  
Vol 47 (1) ◽  
pp. 369
Author(s):  
G. Scott ◽  
C. Ammundsen
Keyword(s):  
Coal Seam ◽  
Environmental Protection Agency ◽  
Poor Quality ◽  
Gas Production ◽  
End User ◽  
Protection Agency ◽  
Coal Seams ◽  
Coal Seam Gas ◽  
Gas Industry ◽  
Access To Water

Access to water is a significant issue in Queensland as much of the State continues to be affected by a prolonged drought. Coal seam gas production involves extracting water from coal seams to reduce the groundwater pressure that keeps the methane trapped in the coal. This process produces large volumes of water. Local councils, primary producers and industrial developers are potential end users of this water; however, if the water is of poor quality, it may be unsuitable for release in the environment and for other direct beneficial uses.This paper examines the complex legislative and regulatory hurdles that need to be overcome before any mutually beneficial agreement between the coal seam gas producer and end user may be completed. It also examines an operational policy recently released by the Queensland Environmental Protection Agency that proposes a framework for the regulation and management of water extracted from coal seams.

Vertical gas migration associated with coal seam gas production

2016 ◽  
Vol 56 (2) ◽  
pp. 602
Author(s):  
Ludovic Ricard ◽  
Julian Strand
Keyword(s):  
Coal Seam ◽  
Risk Evaluation ◽  
Critical Role ◽  
Gas Production ◽  
Mitigation Strategies ◽  
Gas Migration ◽  
Coal Seam Gas ◽  
Gas Reservoirs ◽  
Gas Leakage ◽  
Migration Pathways

Gas migration outside coal seam gas reservoirs has been identified as a risk associated with CSG production. While such an event has not been reported or scientifically associated with CSG production, understanding the physical mechanism of the vertical migration in the overburden involved should gas leakage occur would improve mitigation strategies and risk evaluation. In this extended abstract, a series of key modelling scenarios of gas migration above the reservoir are developed. Interpretation of the scenarios highlights that: the seal/leakage nature of the overburden strongly impacts gas migration and volume of gas leaked; when leakage does occur, the leaked volume represents a very small portion of the original gas in place and volume of gas produced; the connectivity of the overburden plays a critical role on the gas migration pathways and volume of gas leaked; and, residual gas saturation, and relative permeability hysteresis provide means to trap the mobile gas, significantly reducing the volume of gas leaked reaching shallower formations.

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